1. Field of the Invention
The present invention relates to devices and methods for marking road surfaces and, more particularly, to devices and methods for creating road markings of various patterns including markings having varying thicknesses across their widths for increased reflectivity.
2. Description of the Related Art
The surfaces of roads, highways, parking lots and the like (hereinafter "road surfaces") are commonly marked with lines, stripes and other indicators (hereinafter "road markings") for designating traffic and parking lanes, and for similar purposes. To improve the visibility of such road marking s during low-light and nighttime conditions, the markings are commonly formed using reflective materials, including small glass beads that are frequently deposited over the road markings shortly after the markings are applied to a road surface (and before the markings dry or cure)
To further increase the reflectance of road markings, it is known to form multiple steps or tiers in the markings, where adjacent tiers are connected by an inclined or sloping section. These tiered and sloping sections, referred to in the trade as "profiles," constitute retroreflective surfaces that generally reflect light into the line of sight of oncoming traffic. Road markings of this type are commonly formed using a road marking device comprising a material hopper, a floor gate, a pair of side runners and a vertically oriented shutter. In use, the side runners are dragged along, and support the hopper above, the road surface. The floor gate is positioned adjacent to an outlet extending through a bottom side of the hopper and, in its closed position, covers the outlet and prevents marking material from flowing therethrough. When the floor gate is moved away from the outlet, marking material flows through the outlet and onto the road surface between the pair of side runners. The runners thus serve both to provide sliding support for the device as well as to provide side forms which limit lateral flow of the marking material and thereby define the side edges of the road marking. The tiers are formed in the road marking (i.e., the thickness of the road marking is intermittently varied along its length) by adjusting the height of the vertically oriented shutter, which is positioned between the side runners of the device and rearwardly of the hopper outlet. If the shutter is arranged, for example, such that its bottom edge is spaced an eighth of an inch from the road surface, the shutter will permit only one-eighth of an inch of marking material to pass thereunder, thus yielding a road marking having, at that location, a uniform thickness of approximately one-eighth of an inch. Changing the elevation of the shutter as the device is advanced along the road surface results in the inclined or sloped sections mentioned above.
Although suited for its intended purpose, the device described immediately above can produce road markings having only limited profile patterns (i.e., the aforementioned multi-tiered patterns), where the thickness of the road marking at any given point is generally constant across its width.
There is also known a method for applying a road marking where the thickness of the marking is varied across its width to increase the reflectivity of the road marking while preventing water from accumulating along the edges thereof during wet conditions. However, the numerous steps associated with this method render it difficult and expensive to implement. These steps include applying a traffic stripe to a road surface, applying a reflective material to the traffic stripe, applying an anti-adhesion agent to prevent adhesion between the applied traffic stripe and a deformation means passing over it, and then deforming the traffic stripe using a rotatable wheel having a plurality of projections or teeth around the periphery thereof to form spaced grooves in the traffic stripe. This method is also disadvantaged in that the grooves formed in the road stripe are a function of the tooth pattern on the rotatable wheel. Thus, when it is desired to change the pattern of the grooves formed in the road stripe, the tooth pattern on the rotatable wheel must somehow be changed, or a different rotatable wheel must be employed.
What is needed is a device and method for producing night-visible road markings having profile patterns in addition to the multi-tiered patterns discussed above, where the additional profile patterns would increase the reflectivity of the road marking during low-light and night time conditions. Preferably, such patterns could be formed in a single pass of the device over the road surface, and the profile patterns could preferably be varied "on the fly" without requiring equipment changes.